Device for plasma depositing of thin layers onto substrates

ABSTRACT

Improved device for depositing under vacuum thin layers onto substrates comprising a vacuum container and a cylindrical hollow body lined on its inside with the substance to be deposited. A high-frequency electromagnetic field is concentrated inside said hollow body by two conductive cylinders connected to a highfrequency exciting means, promoting a plasma inside said hollow body in presence of an injected gas at a predetermined low pressure.

United States atent 1 1 Van Cakenberghe 1 June 3, 1975 [54] DEVICE FOR PLASMA DEPOSITING 011* 3,264,508 8/1966 Lai et a]. 219/121 P X S BST ATES 3,472,679 10/1969 Ing, Jr. et al.. 117/93.1GDX THIN LAYERS ONTO U R 3,736,175 5/1973 Carleton 118/495 X [75] Inventor: Jean Van Cakenberghe, Beersel,

Belgium FOREIGN PATENTS OR APPLICATIONS A ig eez Compagnie lndustriene des Germany Tellecommunications CIT-Alcatel,

Paris, France Primary ExaminerMorris Kaplan [221 Filed. July 9 1974 Attorney, Agent, or FirmSughrue, Rothwell, Mion,

' Zinn and Macpeak [21] Appl. No.: 486,933

[30] Foreign Application Priority Data [57] ABSTRACT July 13, 1973 France 73.25855 Improved device for depositing under vacuum thin layers onto substrates comprising a vacuum container [52] US. Cl. t. 1l8/ 9-1; 313/2313 and a cylindrical hollow body lined on its inside with [51] Int. Cl. C23c 13/12 th bstance to be deposited. A high-frequency elec- [58] Field of Search ll8/48-49.5; tromagnetic field is concentrated inside aid hollo l 17/ 0 body by two conductive cylinders connected to a high- 219/383, 10.49, 121 P; 3133/2313; 5 frequency exciting means, promoting a plasma inside 1 said hollow body in presence of an injected gas at a [56] References Cited predetermined low pressure.

- UNITED STATES PATENTS 3,211,548 10/1965 Scheller et a1. 117/931 PF x 7 Clams 3 Drawmg Flgul'es SHEET PATENTED JUN 3 I975 DEVICE FOR PLASMA DEPOSITING OF THIN LAYERS ONTO SUBSTRATES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention concerns an improvement to devices for depositing thin layers under vacuum.

2. Description of the Prior Art A device enabling the obtaining of high depositing speed for chemical compounds and consuming relatively low energy is known. Such a device comprise essentially, inside a vacuum chamber, a hollow body lined on the inside with the substance to be deposited. That hollow body is fed from its bottom part by a gas pipe keeping the hollow body at a predetermined pressure. At its upper part, the hollow body is drilled with an outlet opening arranged facing the substrate to be coated. An electromagnetic field is induced inside the hollow body by means of an induction coil placed on the outside of the vacuum chamber surroungind quite closely the said cavity. If the coil is connected to a highfrequency voltage source, a plasma leading to the forming of an arc causing, in its turn, a great rise in temperature inside the cavity leading to a progressive volatilization of the inner wall of thathollow body, is formed inside the hollow body, in contact with the gas injected into that hollow body. The distilled material escapes through the outlet opening placed facing the substrate and is deposited on the latter. Such a device may be usedfor the depositing of chemical compounds and for the depositing of simple substances. In the latter case, the gas used is a neutral gas.

In such a device, the walls of the hollow body constitute a heat shield.

However, in the'case of prolonged operation, the wall of the vacuum. chamber placed in the vicinity of the hollow body has a tendency to heat up and may suffer damage. Moreover, even if the energy output is improved in relation to that of previously known devices, nevertheless, only a part of the electromagnetic flux set up ty the induction circuit enters the hollow body.

Moreover, in certain industrial applications, it is necessary to increase the diameter of the chamber and of the induction coil; the result of this is an increase in the gap between the induction coil and the hollow body, causing an increase in the losses of electromagnetic energy and a decrease in the output.

SUMMARY OF THE INVENTION The aim of the invention is therefore to give the device described hereinabove a more industrial character, making it possible to proceed with deposits with a very high intensity of plasma while maintaining a greater output than that of known devices.

The object of the invention is therefore a device making it possible to deposit this layers under vacuum onto a substrate, comprising:

a chamber kept under vacuum, limited by an insulating wall one part of which is cylindrical;

a cylindrical hollow body arranged axially in the cylindrical part of the chamber, lined on its inside with the substance to be deposited and connected to a source of gas arriving in the hollow body at a predetermined pressure;

an induction coil placed on the outside of the-chamber, arranged round the cylindrical part of the chamber, in the vicinity of the latter, at the height of the hollow body and connected to a highfrequency voltage source;

means for concentrating the electromagnetic field inside the hollow body;

cooling means; characterized in that the main means for concentrating the electromagnetic field inside the hollow body is formed by two concentric conductive cylinders electrically connected together, constituting the secondary winding of an impedance transformer whose primary winding is formed by the induction coil.

The secondary winding of the impedance transformer comprises two coaxial conductive cylinders having a height substantially equal to that of the hollow body, the outer cylinder being situated in the immediate vieinity of the wall of the chamber inside the latter; the two cylinders are split along a radial plane determining two lips on each of the two cylinders. The homologous lips are connected together by two portions of conductive radial planes. 1

The result of this is an increase in the density of the electromagnetic energy inside the hollow body.

A great proportion of theelectromagnetic energy contained in the volume limited by the induction coil is therefore concentrated inside the hollow body.

The invention will be described hereinafter with reference to the accompanying drawings among which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a longitudinal cutaway view of an embodiment of the device according to the invention;

FIG. 2 is a transversal cutaway view of the same embodiment;

FIG. 3 is a diagrammatic cutaway view of another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, it will be seen that the vacuum chamber I3 comprises a cylindrical part 1 extended at its upper part by a part 2 flared upwards and by a cylinder 3 having a greater diameter than the cylindrical part I; that cylinder 3 is connected to the plate 4 of a vacuum chamber by means of a seal 5.

The substrate or substrates and the substrate supports are placed in that vacuum chamber (not shown).

The cylindrical hollow body 6 lined on the inside with the material 7 to be deposited on substrate is arranged in a known manner in the axis of the cylindrical part 1 of the vacuum chamber 13. The upper part of the hollow body 6 comprises an opening 8 arranged facing the substrate. At its lower part, the hollow body 6 is connected to a pipe 9 which crosses through a removable stopper 10 by means of the O ring 11. The pipe 9 itself is connected to the gas source supplying the required gas at a predetermined pressure (for example, from a few hundredths to a few tenths of a torr).

At the height of the cylindrical hollow body, it will be observed that there is, on the outside of the cylindrical part of the vacuum chamber, an induction coil 12 connected to a high frequency voltage source (not shown). At the same height, on the inside of the cylindrical part of the chamber, a cylinder 14 made of a material which is a good conductor (copper for example) is arranged according to the present invention. A second concentric cylinder 15, arranged in the immediate vicinity of the hollow body 6 is cooled by a fiow of water 16.

FIG. 2 makes it easier to understand the electrical connection set up between the cylinders 14 and 15. That figure shows diagrammatically at 20 the highfrequency voltage generator not shown in FIG. 1 which feeds the induction coil 12 and is placed on the outside of the cylindrical wall 1 of the vacuum chamber. In the vicinity of that wall, there is the conductive cylinder 14 split along a radial half-plane 17, shown by discontinuous lines. In this way, that cylinder has two lips 18 and 19. The cylinder 15 is split along the same radial halfplane 17 making two lips 21 and 22 appear; the homologous lips 18 and 21 on the one hand and 19 and 22 on the other hand are connected together by two portions of radial conductive planes 23 and 24. In this way, if the induction coil sets up a field inducing, on the cylinder 14, currents going in a clockwise direction, the cylinder 15 has currents in an anti-clockwise direction flowing through it.

A very great proportion of the electromagnetic energy appearing in the volume comprised inside the induction coil is concentrated inside the cylindrical hollow body.

The two cylinders 14 and 15 therefore actually fulfill the function of electromagnetic energy concentrators.

Moreover, these cylinders play a great part:

It is known that the material 7 lining the wall 6 of the hollow body is progressively volatilized and that the temperature of the wall 6 is high, so that it radiates in its turn. That radiations is absorbed, in the device according to the invention, by the cylinder 15 made of thick copper (4mm, for example). That quantity of heat is immediately dissipated by the cooling circuit 16 and therefore the cylindrical wall 1 of the chamber is not heated. It is now possible to make it with a material which is less refractory than quartz used up till now and it is possible to use glass, to great advantage, for making it.

The system for concentrating electromagnetic energy may, moreover, be completed as follows:

A cylinder 26 (FIG. 1) arranged below the cavity sets up, by induction, a field which tends to push the electromagnetic field back towards the cavity. A cylinder 27 (FIG. 1) fulfills the same functions above the hollow body.

Finally, the electromagnetic field is confined in the volume of the cylindrical hollow body by means of the combined action of the cylinders 14 and 15 and of the cylinders 26 and 27.

The cylinders 14 and 15 constitute the secondary winding of a transformer whose induction coil 12 forms the primary winding and act as an impedance transformer adapted to the cavity.

For the dissipation of energy to be minimum, it is an advantage to make the slot of the cylinders 14 and 15 in the plane 17 as narrow as possible. In the device produced, the gap between the two lips 18 and 19 does not exceed a millimetre.

Besides the advantages already listed, that device has other qualities: It is often an advantage to impart to the cylindrical wall 7 a great diameter without modifying the volume of the hollow body. But then, the gap between the wall of the chamber and the hollow body is increased and hence the losses are increased. By means of the cylinders 14 and 15, it is possible to keep the induced power constant and to increase the diameter of the induction coil without increasing losses. The diameter of the cylinder 14 and the length of the 2 portions of radial planes 23 and 24 will be increased without modifying the diameter of the cylinder 15 or the volume of the hollow body. The required increase of the outer diameter has therefore actually been effected without reducing the density of energy inside the hollow body.

It should be observed, moreover, that in that case, the solid angle at which the material may be deposited onto the substrate from the outlet opening 8 of the cylindrical hollow body is no longer limited by the wall of the chamber and may therefore be increased. It is then possible to coat a substrate having a greater surface and to obtain at the same time a more homogenous coating.

FIG. 3 shows diagrammatically an industrial device according to the invention. An induction coil 32 fed by a high-frequency voltage source 33 is arranged around a cylindrical chamber 31 having a large diameter. A split cylinder 34 made of a conductive metal analogous to the preceding cylinder 14 may rotate on itself within the chamber about a central axis 35. As previously, the cylindrical hollow body 36 made of a material to be sprayed is surrounded by a split cylinder 37. As previously, the homologous lips of the slots of two cylinders 34 and 37 are connected together by portions of plane conductors 38 and 39. The cylinder 37 is cooled by a water pipe 40, shown in discontinuous lines, fed from an axial column 41.

The assembly constituted by the hollow body 36, the inner cylinder 37, the water pipe 40, may rotate about the axis 35 at the same time as the cylinder 34. In this way, the opening of the cylindrical hollow body 36 is placed successively facing the substrates 42, 43, 44, spaced regularly in a circle and lastly facing an elongated substrate 45 before which the opening of the hollow body 36 passes slowly at a constant speed, thus providing a very homogenous coating on the whole of the substrate 45.

The effect of concentration of the electromagnetic field is obtained as previously, as the electromagnetic field prevailing between the cylinder 37 and the cylinder 34, is negligible.

What is claimed is:

1. Device for vapor depositing a thin layer under vacuum onto a substrate, comprising:

a chamber kept under vacuum, limited by an insulating wall, one part of which is cylindrical;

means supporting at least one substrate in an upper section of said chamber;

a cylindrical hollow body arranged axially in the cylindrical part of the chamber, lined on its inside with the substance to be deposited, connected to a source of gas arriving in the hollow body at a predetermined pressure and in alignment with said at least one substrate;

an induction coil placed on the outside of the chamber, arranged round the cylindrical part of the chamber, in. the, vicinity of the latter, at the height of the hollow body and connected to a highfrequency voltage source whereby to generate a plasma to evaporate said substance;

means for concentrating the electromagnetic field inside the hollow body formed by two concentric conductive cylinders (14 and 15) electrically connected together, constituting the secondary winding of an impedance transformer whose primary winding is formed by the induction coil; and

means to cool said cylindrical hollow body.

2. Device according to claim 1, wherein the two concentric cylinders are split by a radial half-plane (17).

the homologous lips being connected together by por-- tions of conductive radial planes (23 and 24)so that the two'concentric conductive cylinders (14 and constitute a single circuit.

3. Device according to claim 2, one of the concentric conductive cylinders (14) being arranged in the immediate vicinity of the wallet the cylindrical hollow body (6) and the second conductive cylinder (15) being placed in the vicinity of the wall 1 of the vacuum chamber (13). I

4. Device according'to'claim 3, wherein the concentric conductive cylinder (14) placed in the vicinity of the cylindrical hollow body is cooled by a water pipe (16). v

5. Device according to claim 4, wherein the electromagnetic field concentration means additionally comprises a conductive cylinder (26) arranged in vicinity of the wall (1) of the chamber (13), inside the latter, below the hollow body (6).

6. Device according to claim 5, wherein the concentration means additionally comprises a conductive cyl inder (27) arranged in the vicinity of the wall (I of the chamber (13) above the hollow body (6).

7. Device according to claim 1 wherein:

means support a plurality of substrates in a spaced annular array in said upper section of, and about the axis of, said chamber, a cylinder generated through said annular array passing through said hollow body; and

further means rotatably support said hollow body and concentrating means whereby said hollow body is orbited in a path in sequential alignment with said plurality of substrates to effect said depositing on each substrate. 

1. Device for vapor depositing a thin layer under vacuum onto a substrate, comprising: a chamber kept under vacuum, limited by an insulating wall, one part of which is cylindrical; means supporting at least one substrate in an upper section of said chamber; a cylindrical hollow body arranged axially in the cylindrical part of the chamber, lined on its inside with the substance to be deposited, connected to a source of gas arriving in the hollow body at a predetermined pressure and in alignment with said at least one substrate; an induction coil placed on the outside of the chamber, arranged round the cylindrical part of the chamber, in the vicinity of the latter, at the height of the hollow body and connected to a high-frequency voltage source whereby to generate a plasma to evaporate said substance; means for concentrating the electromagnetic field inside the hollow body formed by two concentric conductive cylinders (14 and 15) electrically connected together, constituting the secondary winding of an impedance transformer whose primary winding is formed by the induction coil; and means to cool said cylindrical hollow body.
 1. Device for vapor depositing a thin layer under vacuum onto a substrate, comprising: a chamber kept under vacuum, limited by an insulating wall, one part of which is cylindrical; means supporting at least one substrate in an upper section of said chamber; a cylindrical hollow body arranged axially in the cylindrical part of the chamber, lined on its inside with the substance to be deposited, connected to a source of gas arriving in the hollow body at a predetermined pressure and in alignment with said at least one substrate; an induction coil placed on the outside of the chamber, arranged round the cylindrical part of the chamber, in the vicinity of the latter, at the height of the hollow body and connected to a high-frequency voltage source whereby to generate a plasma to evaporate said substance; means for concentrating the electromagnetic field inside the hollow body formed by two concentric conductive cylinders (14 and 15) electrically connected together, constituting the secondary winding of an impedance transformer whose primary winding is formed by the induction coil; and means to cool said cylindrical hollow body.
 2. Device according to claim 1, wherein the two concentric cylinders are split by a radial half-plane (17), the homologous lips being connected together by portions of conductive radial planes (23 and 24) so that the two concentric conductive cylinders (14 and 15) constitute a single circuit.
 3. Device according to claim 2, one of the concentric conductive cylinders (14) being arranged in the immediate vicinity of the wall of the cylindrical hollow body (6) and the second conductive cylinder (15) being placed in the vicinity of the wall 1 of the vacuum chamber (13).
 4. Device according to claim 3, wherein the concentric conductive cylinder (14) placed in the vicinity of the cylindrical hollow body is cooled by a water pipe (16).
 5. Device according to claim 4, wherein the electromagnetic field concentration means additionally comprises a conductive cylinder (26) arranged in vicinity of the wall (1) of the chamber (13), inside the latter, below the hollow body (6).
 6. Device according to claim 5, wherein the concentration means additionally comprises a conductive cylinder (27) arranged in the vicinity of the wall (1) of the chamber (13) above the hollow body (6). 